#include <stdio.h>

int main() {
    int arr[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
    int k = 0;
    scanf("%d", &k);
    int sz = sizeof(arr) / sizeof(arr[0]);
    int left = 0;
    int right = sz - 1;
    while (left <= right) {
        int mid = (left + right) / 2;
        if (arr[mid] < k) {
            left = mid + 1;
        } else if (arr[mid] > k) {
            right = mid - 1;
        } else {
            printf("找到了，下标是%d\n", mid);
            break;
        }
    }
    if (left > right) {
        printf("找不到了\n");
    }
    return 0;
}
